Newly occurring partial recording problem

I'm having a problem with occasional partial recordings that seems to have started in the last month or so. The common pattern seems to be as follows:



I start watching a recorded show while another show is recording.

I occasionally FF or REW the show I'm watching.

At some point I notice that the show being recorded has stopped recording, with no warning. (Red light is now off.) If I check that just stopped recording, it shows as (partial). It has not restarted recording; it's as if the recording was manually stopped (it was not).



I don't know if this is a factor, but for the most recent occurrence of this issue, the recorded show I was watching and the show that was prematurely stopped were both on the same channel. (In this case, KNTVDT, the HD version of the local NBC affiliate.) As far as I know this problem hasn't occurred while I was away (that is, while I am not watching or interacting with the TiVo).



Has anyone seen this before, or can you offer troubleshooting clues? In particular, is there any way to get to some diagnostic info that would explain the reason for the cancelled recording?



Note that I have just restarted the box, and will continue to monitor the situation.



I have a stock 2-tuner Premiere XL, with Comcast service, using a CableCard.



Thanks, all,

- Mitch